Tag Archives: health

How to stop crutches from clicking

Adjustable-length metal crutches click with each ground contact and lifting, which some people find annoying. The reason for the clicks is that the push button used to adjust the length of the crutch is not snug in its hole, but pushes against the top of its hole when the crutch is pressed against the ground and against the bottom of the hole when the crutch is lifted.

The push button length adjustment system consists of two pipes inside each other, with holes in the outer pipe and a spring-loaded button on the inner one. Pushing the button in allows the pipes to slide relative to each other. When the button is released and pops out into a hole, it locks the pipes together. Similar push button systems are used to adjust the handle length of rolling luggage and the weight stacks of gym equipment.

To silence the clicks, the button should push against the same side of the hole at all times, which can be achieved by adding one spring. The spring should pull the inner pipe of the adjustable part of the crutch in the direction of shortening the crutch, i.e. the same direction as ground contact. Then the button always stays in contact with the same side of its hole instead of alternately hitting the two opposing sides. The reason the spring should pull in the same direction as ground contact is that the upward force on the adjustable inner pipe when the crutch bears the weight of the user is much greater than the downward force of the weight of the inner pipe when the crutch is lifted. Thus it is easier to overcome the downward force using a spring.

A homemade version of the spring is to tie a rubber band under tension to above and below the adjustment button. A bungee cord or bicycle inner tube would work as well.

The length adjustment of the crutch with a spring would be similar to that of an office chair – automatic in one direction, but requiring force in the other. When the button is pushed, the crutch shortens automatically by one hole. To lengthen the crutch, one has to push the button in and then pull the crutch in two opposing directions.

Pill testing, placebos and illegal market efficiency

Testing illegal drugs for the active ingredient differs from testing for poisonous adulterants. Both tests have opposite effects on drug use before and after buying. After the pill has been purchased, testing reduces use, because sometimes the drug fails the test, whether correctly or not, and is discarded. Before purchase, the option to test for and avoid adulterated or inactive drugs reduces the buyer’s risk, thus increases use.

In the longer term, testing benefits the dealers of purer, more predictable and less toxic drugs, putting some suppliers of fakes out of business. Pill predictability reduces overdoses – a health effect similar to lower toxicity. If old drugs can be tested, but new ones not, then buyers experiment less and the incentive to invent new narcotics decreases.

The avoidance of poisonous adulterants is good for public health, but purer pills not necessarily so. Inactive drugs undermine consumer confidence in the illegal market, reducing use, prices and casual purchases. Trust then requires a long-running relationship with the seller, which has multiple benefits. It motivates dealers to care about the health of their loyal customers, simplifies policing and gives researchers and social workers better long-term access to the at-risk population.

One claimed benefit of party drugs is that they reduce anxiety, increase the user’s confidence and social interaction, thus improving mental health. Evidence from psychiatric medicines suggests that many such benefits are due to the placebo effect. Users are quite inaccurate in estimating the purity of ingested drugs, and factors like price and place of purchase strongly influence their perception of purity. The price per pure gram is negatively related to purity in some markets, further supporting the placebo interpretation. If inactive pills boost confidence similarly to illegal drugs, then there is a clear case for flooding the market with harmless placebos. The availability of pill tests for the active ingredient reduces this opportunity to make the illegal market inefficient. Tests for toxic adulterants, however, actually favour harmless placebos.

Shoe and clothing thickness is not optimally distributed

Shoes are typically of thinner material in the toes than around the ankle, but human toes are more cold-sensitive than ankles, because toes have a greater ratio of surface area to volume (thus greater heat loss) and are further from the core of the body, so get less warm blood supply. Similarly, pants are usually thicker on the butt (due to pockets) or the upper end in general (suit pants lined to the knee), in spite of the legs requiring more warming than the pelvic region. Suit jackets are open on the chest, but overlap on the belly, which needs less extra insulation. The same suboptimal distribution of warmth characterises various V-necked upper body clothes. Jackets are also thicker on the front than the back, despite most people’s backs being more cold-sensitive than bellies.

This impractical design can be explained for men’s jackets by the desire to improve the wearer’s looks with the visual illusion of broad shoulders created by the V-shape of the front of the jacket. I have written about this in more detail: https://sanderheinsalu.com/ajaveeb/?p=885

For other clothes and shoes, there seems to be no reason for the suboptimal distribution of thickness, which would be easy to fix in the manufacturing process. The extra layers of cloth added by pockets could be balanced by using thinner cloth to make the pocket area of the pants. The pocket pouches on jeans for example are usually of thin cloth, which is a step in the right direction. However, the surface of the pants covering the pockets is usually of the same cloth as the legs. Lining could easily be added to trouser legs to make these as thick as the upper part, compensating for the extra layer of cloth by manufacturing the trousers out of thinner material overall. Similarly, adding a layer to the back of a jacket is easy.

The only difficult part to compensate in the impractical thickness distribution of clothing is the thin chest cover (relative to belly and back) of a V-neck jacket, but this difficulty only arises from the desire to preserve the look of a V-neck. A similar visual illusion of broad shoulders could be created by painting a V-shaped pattern on the garment.

A different impractical aspect of shoe design that can be explained by fashion is the pointy toes. The tapering tips create an optical illusion that makes the feet seem longer, which does not necessarily improve the wearer’s looks. However, fashion is frequently ugly, as evidenced by the web search results to the phrase: „it’s called fashion, look it up”.

Lifting weights a smaller distance may be more intense exercise

Somewhat counterintuitively, moving a part of the body a greater distance may be easier in some cases. For example, lying on your back and lifting straight legs off the floor, the muscles work harder when the legs are close to the floor than when they are close to vertical. Leg lifts lying on your back are easier when their amplitude is larger (90 degrees as opposed to 45 degrees off the ground).

In many exercises, lifting the limb to an easier position gives the muscles a rest, making the workout less intense (calories burned per unit of time) overall. Examples are biceps curls until the forearm is vertical, straight arm raises all the way overhead, deadlifts to a straight or even backward tilting posture, as opposed to stopping partway through. Slower movement may make an exercise more intense by spending more time in an effortful position, e.g. slow push-ups or squats.

Lifting a longer distance may also make an exercise easier by giving a greater opportunity to swing the limb and use inertia, which is usually bad technique. For example, standing leg lifts to the front take less effort when the leg starts from behind the body and is already moving when passing vertical, compared to starting from holding the leg slightly to the front of the body.

Pre-selected health insurance plans for visitors

A half-year visit to a US university under a J1 visa requires US health insurance. In the University of Pennsylvania, the website of the International Students’ and Scholars’ Office says that they have pre-selected some health insurance plans. According to their cover description and comparison websites, these plans offer significantly less cover than similarly-priced plans not pre-selected by U Penn. My spreadsheet comparing the health insurance options is public. Possibly I have missed some aspects of insurance that justify the price difference. Another explanation is that the pre-selection was done by people who do not themselves use these insurance plans (because they are not visitors to the US) and have little incentive to make an effort to choose the best plan. A more negative and less likely interpretation is that the insurance company is providing incentives (such as kickbacks) for the selectors at U Penn to direct visitors to expensive low-cover plans that are profitable for the insurer.

Arranging a virgin birth in a low-tech way

Warning: this Christianity- and Christmas-themed post may offend or disgust. The procedure described is unpleasant for the receiver.

Fertilisation of an egg cell requires sperm to reach it, which does not require breaking the hymen. A thin tube, such as a hollow straw or reed, can be inserted through the small opening in the hymen to pump sperm (obtained via male masturbation) into the vagina. The simplest way to pump the sperm is to suck it into the straw with one’s mouth and then blow it out. Another way is with an enema pump (bulb syringe) that can be constructed with primitive technology: a hollow leather ball glued to a reed using resin, tar or bone glue. The seams of the leather ball can be waterproofed with tar. The ball can be made to spring back into shape after squeezing, e.g. by constructing it with wire hoops or springs inside.

Successful fertilisation with the above method likely requires many attempts, because the probability of pregnancy from unprotected sex during the most fertile part of the menstrual cycle is 30%. Sexual activity causes hormonal changes in the female organism that facilitate fertilisation, which a simple reed insertion probably does not, but it may be possible to create similar hormonal changes with an erotic massage.

The above method can be used to arrange a virgin birth in a primitive society. No miracles are required, although a virgin giving birth may be marketed as miraculous.

Modern in vitro fertilisation technology of course expands the range of ways to engineer a virgin birth.

Protecting a wound or burn that needs frequent access

If it is necessary to put cream on a burn frequently, then a band-aid is inconvenient, because it must be pulled off every time. Also, a band-aid may stick to an oozing wound and reopen it every time it is pulled off. If the damaged skin needs covering, for example because the weather requires thick clothes, then one solution is to stick or tie a small cup-shaped object on top of the wound. Tying is preferable, because removing a stuck object again irritates the damaged area. The edges of the cup should be soft, because these press on the skin (so a plastic bottle cap is a bad idea). One soft-edged approximately cup-shaped object is the eyepiece of swimming goggles.

Swimming goggles protecting wound

The eyepiece is nicely attached to adjustable straps for tying it on with neither too much nor too little pressure. The eyepiece may be flipped over to the side to get access to the damaged skin.

Of course, the location of the wound may cause difficulties in tying swimming goggles on top of it, e.g. on the torso. Even on the arm or the leg, the lengthwise movement of the sleeve or pant leg may push the goggles off, because the strap running around the limb does not resist lengthwise movement well. Then adding some bandages may be necessary.
Overnight, the area under the goggles gets sweaty. To avoid this, small air holes may be drilled in the eyepieces, which of course makes the goggles useless for swimming.

Ways in which an eater can get negative calories from food

There are at least four ways in which an eater may have less energy and nutrients after consuming a food: mechanical, chemical, physical and biological. The mechanical way is that chewing and other parts of digestion take energy, so if a food requires serious mastication and contains few calories, then more energy may be spent than absorbed. This has been claimed for raw celery.
Chemically, one food may react with another in a way that makes one or both of them less digestible. The less effective absorption reduces the nutrients obtained compared to not eating the second reactant. The chemical pathway to inefficient digestion may have multiple steps. For example, ascorbic acid leaches calcium from the body, and calcium is required for the absorption of vitamin D, so eating more citrus fruits may indirectly reduce one’s vitamin D levels.
When calculating the calorie content of food, indigestible fibre is subtracted from carbohydrates before adding up the energy obtained from carbohydrates, fats and proteins. However, if fibre reduces the absorption of calories (in addition to its known reduction of the absorption iron, zinc, magnesium, calcium and phosphorus), then the food’s bioavailable calorie content is less than that obtained by simply subtracting the fibre. To derive the correct calorie content, the fibre should then have negative weight in the calculation, not zero. This difference may explain why in Western countries, a high-fibre diet predicts better health in multiple dimensions in large prospective studies (Nurses’ Health Study, Framingham Heart Study), controlling for calorie intake, lifestyle and many other factors. If the calorie absorption is overestimated for people eating lots of fibre (because the calorie intake is larger than the absorption), then their predicted health based on the too high calorie estimate is worse than their actual health. This is because most people in Western countries overeat, so eating less improves health outcomes. If the predicted health is underestimated, then the high-fibre group looks unusually healthy, which is attributed to the beneficial effects of fibre, but may actually be due to absorbing fewer calories.
A food may chemically break down tissues, e.g. bromelain and papain, from fresh pineapple and papaya respectively, denature meat proteins, so cause mouth sores. Rebuilding the damaged tissue requires the energy and nutrients, the quantity of which may exceed that absorbed from the food.
Chemically causing diarrhea reduces the time that foods (including the laxative agent) spend in the gut, thus reduces nutrient absorption.
Stimulants like caffeine speed up metabolism and cause greater energy expenditure, but may give zero calories themselves, resulting in a net negative caloric balance.
Just like chemical damage, physical injury to the body necessitates spending calories and nutrients for tissue repair. For example, scratchy food (phytoliths, bran) may cause many microscopic wounds to the digestive tract.
Cold food requires the body to spend energy on heating, so if the calorie content is small, then the net energy obtained is is negative. Examples are ice cubes and cold water.
A food substance may physically partially block the absorption of another, for example a gelling agent (methylcellulose, psyllium husks) may turn a juice into a gel in the gut and thereby reduce its absorption. Based on my personal experience, psyllium husks gel liquid feces, thus effectively reducing diarrhea. Mixing psyllium husks with carrot juice and with asparagus powder dissolved in water before consuming them during the same meal results in the excretion of separated faint orange and green gels somewhat distinct from the rest of the feces (photos available upon request, not posted to keep the blog family-friendly). This is suggestive evidence that the gelling agent both kept the juices from mixing in the gut and reduced the absorption of the colourful compounds by keeping the juice in the centre of the gel away from the intestinal wall.
Biologically, a food may reduce the nutrients available to the organism by causing infection, the immune response to which requires energy and depletes the body’s reserves of various substances. Infection may lead to diarrhea, although the mechanism is chemical, namely the toxins excreted by the microbes. Infection with helminths (intestinal worms) that suck blood through the wall of the gut requires the replenishment of blood cells, which uses up calories, protein and iron.
If the food takes a long time to chew or is bulky, then chemical and electrical signals of satiation are sent from the gastrointestinal tract to the the appetite centre of the brain. These signals reduce the desire to eat, thus decrease calorie intake.

Recovering faster from a sprint by jogging than by walking

It seems that the panting and muscle weakness right after a sprint passes faster when I jog than when I walk or stand (the recovery I am talking about here is the minutes it takes to get back to normal breathing, not the days it takes for muscle soreness to disappear). I did not find empirical research on whether jogging actually speeds recovery from a sprint – it could be just my false perception. For this blog post, I will assume my perception is correct and speculate about why.
Faster recovery of breath when jogging seems counterintuitive, because jogging takes more power (energy per unit of time) than walking, so consumes the body’s cardiovascular output and nutrient reserves faster. The increased consumption should delay the short-term recovery. However, the perception of recovery need not be positively correlated with the whole body’s oxygen and glucose consumption, only with the CO2 reaching the chemoreceptors (either central in the brain’s respiratory centre, or peripheral in the carotid arteries and the aorta).
If the blood vessels in the legs expand during a sprint, and the blood pressure falls after a sprint faster than the blood vessels contract, then blood may pool in the legs and less of it may reach the chemoreceptors. Blood is forced up from the legs by the contractions of the leg muscles, which are more intense and frequent during jogging than walking. Therefore jogging may increase the venous return, leading to a better blood supply to the torso and the brain, which the latter perceives as faster recovery from exercise.
Even if the contractions of the leg muscles during jogging and walking had the same intensity and frequency, the group of muscles activated during jogging does not completely overlap with those working during walking. One muscle group may surround the major veins in the legs more closely, thus pump blood up more effectively.
There may be evolutionary reasons why the jogging muscles are better at stimulating venous return – faster overall circulation is needed during more intense exercise, for example when jogging compared to walking. Better venous return speeds up the circulation.
A mechanical reason why jogging may improve recovery from a sprint better than walking is that the jogging muscles overlap with the sprinting muscles more than the walking muscles do. If blood pools in the sprinting muscles and needs to be returned to the core, then contracting the jogging muscles forces blood out of the sprinting muscles better than contracting the walking muscles does.

Rigid skirt to prevent falls

Falls are a major cause of hospitalisation in the elderly and people with impaired balance or strength. A fall may cause a vicious cycle: the bad experience leads to a fear of falling, which makes people avoid exercise. Not exercising leads to worse balance and muscle condition. Weakness and a lack of balance cause more falls.
To prevent falls, people should train their sense of balance and their stabilising muscles, but in a way that does not risk injury via falls during training. One device that would allow practising balance while preventing falling over is a rigid wide-flared skirt attached above a person’s centre of gravity (the attachment could be almost under the armpits). The hem of the skirt would be above the ground when the body is upright, but its edge would touch the ground if the body tilts too much in any direction. Support from the rigid skirt would then prevent further tipping in that direction. The lack of support in a central position (and for slight tilts around it) allows practising balance, for example by standing on one leg and trying to stay upright. The principle is the same as for helper wheels (training wheels) on childrens’ bicycles, which are off the ground while the bike is in a central position, but touch the road and stop too great a tilt to the side once the bike tips away from the centre. Other analogies to the rigid skirt are hands-free crutches pointing in all directions simultaneously, or a walking frame that surrounds the body, as opposed to being pushed in front.
The advantage of the skirt for fall prevention over crutches or a walking frame is that the skirt is hands-free. The advantage over a fixed training frame, or somewhat slack ropes tied to the upper body that also prevent a fall, is that the skirt moves with the person. This makes training easier by allowing walking and jogging.
The skirt can be home-made from many materials, such as tent poles or bamboo sticks tied or duct taped to a belt at the top and a hula hoop at the bottom. Using modern materials such as carbon fiber ski poles can make the skirt light, yet strong and rigid.
Of course the rigid skirt looks strange and attracts notice if not too many people are using it. On the one hand, the skirt does not have to be used in public if in-home training is enough. On the other hand, the first walking frame or the first crutches must also have looked strange to bystanders, but are now accepted mobility aids that almost nobody reacts negatively or even curiously to.
For using the skirt on the street, one problem is the wide-flared base (about 2m in diameter) that makes it difficult to pass other pedestrians. One (expensive) solution is to make the skirt out of sticks that can be moved independently and add a robotic controller that keeps the skirt narrow if the body is upright, but when the tilt angle becomes large enough, flares the skirt out in the direction of the tilt to stop the fall. Flaring the skirt means moving the sticks outward and lengthening them.